1. Field of the Invention
This invention relates to devices for indicating variations in electrical resistance of living bodies and more particularly, human bodies.
2. Prior Art
In the prior art there exist devices for measuring resistance of a living body. Such devices are sometimes referred to as galvonic skin response (GSR) devices and are used in a variety of applications. Such applications include polygraphs and research uses. Examples of such prior art devices are shown in U.S. Pat. No. 3,290,589, U.S. Pat. No. 4,459,995 and U.S. Pat. No. 4,300,574.
Such instruments contained in the prior art have several drawbacks. Firstly, the better instruments have a high power consumption, are very expensive, are very complex, are large and non-portable and have complex and confusing controls. The less expensive and portable units also have other disadvantages. In particular, such disadvantages include high power consumption, poor stability, low sensitivity and an expensive and complex power source. In addition, such more expensive and less expensive devices share certain common disadvantages. In particular, the circuitry is typically noisy, it is difficult to accurately read the position of the controls, it is difficult to maintain stable voltages and no provision is provided for the operator to instantaneously check to determine if the variations in the output readings are the result of changes in the living body or some failure in the equipment without recalibrating the entire device.